Hemorrhage is defined as a flow of blood outside of the normal bloodstream. It can consist of simple bleeding or become massive in certain situations, notably trauma, and lead to a state of hemorrhagic shock associated with a drop in blood pressure.
Various clinical contexts lead to a risk of hemorrhage, such as surgery, trauma, treatment, thrombocytopenia or a constitutional or functional deficiency (such as hemophilia) (Spahn D et al. Critical Care. 2013, 17:R76). In severe hemorrhaging, coagulopathy is observed. The coagulopathy corresponds to the consumption of platelet and coagulation factors. Treatment is essential and the result of the hemorrhage depends on it. Various treatment strategies are currently followed.
One approach consists of using a transfusion support based on fresh frozen plasma (FFP), packed red blood cells or platelets. Nevertheless, the success of the platelet-based approach is limited by several factors, including the accessibility of platelets, their short shelf life (5 days on average), problems related to the conditions of storage, the risk of contamination of certain types of sample, their cost and the risk of inefficacy or even intolerance due to alloimmunization.
Another approach is based on the use of coagulation factor concentrates, such as fibrinogen concentrates and prothrombin complex concentrates (factors II, VII, IX and X). Studies have also suggested the use of factor Vila (NovoSeven®). However this last use is not recommended because of the high rate of induced thrombosis.
Finally, another approach in emergency situations consists of using tranexamic acid, which is a powerful plasminogen activation antagonist and so acts as an antifibrinolytic (Fries D. Transfusion. 2013; 53:91S-95S).
None of the approaches proposed to date enables induction of platelet activation and aggregation during a hemorrhagic episode, although these are key steps in stopping bleeding. When a vascular injury leads to bleeding, a series of steps, referred to as primary hemostasis, is put in place. It involves the platelets, biconvex disk-shaped cells without nuclei approximately 2-5 μm in diameter. Various actors participate in this process, which leads to the formation of a hemostatic clot. The first phase, called adhesion, enables the recruitment of circulating platelets at the site of injury. This step involves the Willebrand factor, collagen and platelet receptors called collagen receptors (GpVI and α2β1). The second phase, called platelet activation, comprises the liberation of pro-aggregant factors and the expression on the platelet surface of proteins such as P-selectin. This phase is followed by the phase called aggregation, which notably involves fibrinogen and the platelet receptor GpIIb/IIIa and the membrane exposure of procoagulant phospholipids enabling the fixation of coagulation factors to the site and eventually the formation of a fibrin/platelet clot and the stopping of bleeding.
It is now well established that the activation of platelets during the process of hemostasis leads to the appearance of two populations of platelets, called pro-aggregant and procoagulant. The latter are characterized by the surface expression of phosphatidylserine, at the origin of thrombin generation. These are called superactivated platelets. Hence we speak of platelet superactivation potential to describe the capacity of each individual to generate this population of platelets in response to agonists such as thrombin and collagen. Recent studies suggest that any therapeutic strategy aiming to induce the appearance of this population of activated platelets shows great potential for the treatment of hemorrhagic situations (Mazepa M et al. ATVB 2013, 33(8):1747-52). Furthermore, their interest is reinforced by data confirming that the hemostatic effect of transfused platelets is dependent on this population. However, the approaches proposed to date are not based on the injection into the bloodstream of physiological or natural platelet activators such as collagen or proteins and peptides derived from collagen claimed in the present invention.
The central role of platelets in stopping bleeding is at the origin of recent work aiming to develop products derived from or mimicking platelets (synthetic platelets). Among the approaches proposed, there is a distinction between those based on products derived from cells, such as thromboerythrocytes and thrombosomes, and those using micrometer-sized particles covered with peptides derived from proteins involved in the platelet activation cascade, such as synthocytes or Fibrocaps™ based on peptides derived from fibrinogen (RGD peptides or dodecapeptide H12), or those covered with peptides binding to Willebrand factor, to collagen and to GpIIb/IIIa (Lashof-Sullivan M et al. Nanoscale 2013, 5, 10719-10728). A hemostatic effect has been described for these particles covered with peptides binding to Willebrand factor, to collagen and to GpIIb/IIIa, which enables an application to be envisaged in the hemorrhagic context. However, this approach poses a major problem of industrialization for this type of product, which combines several peptides on a single particle, with the necessity to master and qualify parameters such as the rate of binding and the ratio for each of the peptides, as well as the stability of the product once injected, without considering the fact that very high doses (of the order of several tens of milligrams per kilogram) must currently be injected (Modery-Pawlowski C et al. Biomaterials 2013:516-541).
There is therefore a need for new means of treatment of hemorrhage that are injectable into the bloodstream to be made available. Preferably these would be easily prepared industrially and able to be used at low concentrations.
With the aging of the population, physicians are more and more frequently confronted with patients treated with anticoagulants and antiplatelet drugs. Although the strategy of temporary withdrawal of these treatments is well-defined for programmed interventions (5-7 days' withdrawal for new antiplatelets drugs and 5 days' withdrawal for new anticoagulants), they seriously complicate the emergency treatment of patients in hemorrhagic situations (surgery or trauma, notably cranial) (Bonhomme F et al. Eur J Intern Med. 2014 March; 25(3):213-20). Various strategies of emergency reversion have been proposed but, for the new antiplatelet drugs, these are mostly limited to transfusion of platelets (Beynon C et al. Crit Care. 2012 Jul. 26; 16(4):228). There is a need for new injectable hemostatic products that are capable of enabling recovery of platelet function during hemorrhagic episodes independently of the mode of action of these new antiplatelet drugs. The fact that the collagen-dependent platelet activation pathway is the most physiological, and is not, to date, modified by any antiplatelet treatment on the market, reinforces the interest of administering proteins or peptides derived from collagen by the systemic route in these situations. It is well established that the binding of GPVI to collagen or the proteins or peptides derived from collagen of the present invention leads to intense signaling within the platelets.
In a logistically constrained context, such as overseas theaters of military operations, the treatment of hemorrhage is governed by the concept of “damage control resuscitation”, notably involving transfusion (packed red blood cells, plasma and platelets). Nevertheless, this situation is characterized by a difficulty of access to these blood products, especially to platelets, requiring an modified treatment, covered by the term “remote damage control resuscitation”, with the use of whole blood as the principal difference (Jenkins D H et al. Shock. 2014 May; 41 Suppl 1:3-12). This strategy, although associated with a risk of contamination, is promising but remains limited to the military domain at present (Murdock A D et al. Shock. 2014 May; 41 Suppl 1:62-9).
The present invention relates therefore to the interest of intravenous administration of platelet-activating proteins or peptides derived from collagen as a new injectable hemostatic in three situations involving hemorrhage:                during an episode of massive bleeding, notably non-compressive, requiring the ability to activate the platelets in the bloodstream;        as an adjuvant during transfusional resuscitation away from a medical center, as a complement to an approach based on the transfusion in particular of whole blood or platelets;        as a reverting agent for new antiplatelet drugs (e.g. prasugrel, ticagrelor), which are currently on the market without antidotes, for surgery or hemorrhage, notably intracranial.        